DARPA's Greatest Inventions

Preventing sleep deprivation

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Credit: Andrew Burton / Getty Images

DARPA's $20 million Preventing Sleep Deprivation (PSD) program aims to find ways for soldiers to stay awake and effective for as long as seven days. Dolphins and whales are providing a promising direction. These mammals survive on something called "hemispheric sleep," a state in which one side of the brain is awake while the other is unconscious.